Diesel engines are becoming more prevalent because of their high efficiency and fuel economy, compared to gasoline engines. Accordingly, demand for such diesel engines is increasing. Diesel engine emissions are also strongly regulated. Therefore many schemes for reducing air diesel engine emissions are being investigated.
One scheme utilizes a plasma reaction. This has been recognized as promising technology because it can reduce oxidized nitrogen (NOx) and diesel particulate matter (PM) at the same time. A streamer corona reaction that is achieved by applying a high voltage to form plasma may be terminated by a spark produced at the streamer. Therefore a method and apparatus for maintaining the formed streamer is needed. Additionally, the reduction of the PM and NOx is not satisfactory in the prior art that utilizes a plasma reaction, and therefore improvements are needed.
In addition, other types of corona-generating apparatuses for forming plasma consume too much power to be used in a vehicle, or the function of corona discharging fails when an electrode is contaminated, by soot for example.